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Pension and Other Benefit Plans - Changes in Accumulated Postretirement Benefit Obligation, Plan Assets and Funded Status (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Change in Plan Assets      
Benefits paid     $ (257)
Postretirement medical plan      
Change in Projected Benefit Obligations      
Projected benefit obligation at beginning of year $ 1,234 $ 1,193  
Service cost 28 31 29
Interest cost 32 36 45
Contribution by plan participants 10 8  
Actuarial (gains) losses (95) 64  
Benefits paid (63) (58)  
Curtailment   (40)  
Projected benefit obligation at end of year 1,146 1,234 1,193
Change in Plan Assets      
Plan assets at fair value at beginning of year 1,356 1,185  
Actual return on plan assets 15 221  
Contributions by plan participants 10 8  
Benefits paid (63) (58)  
Plan assets at fair value at end of year 1,318 1,356 $ 1,185
Asset 172 122  
Amounts Recognized in Accumulated Other Comprehensive Loss      
Actuarial losses 225 186  
Prior service credit 81 104  
Total amount recognized in accumulated other comprehensive income $ 306 $ 290